Electrical logging apparatus



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AAAAAAAAAAAAAAAAAAAAAAAAA US Fi l e d O 0 t l 9 l 9 36 liar I? a/ a 2 E 5/9 gal? 24 l|2-i]| Patented May 23, 1939 I I, UNiT-Eo .fs'r TEsj "PATENT-OFFICE" I uac'rarclu. LOGGING Arman-us 12m Babcock, Duncan, on... mail to Halli- 7 Burton Oil Well cementing Company, Duncan,

Application October 19, 1986, Serial No. 108,351

1 Claim.

' .Examples of these systems are found in the United States Patents to Jakosky, No. 2,038,046

and Martiennsen, ,No. 2,018,080.'

In the electrical logging systems of which I am aware, the measuring or indicating is done by instruments located at the surface of the well and it has been necessary to connect the electrodes or the antennae in the well to the instruments at the surface by means of one or more electrical conductors. These electrical conductors are very expensive. stand wear and tear in the well, lead sheathed cables are'usually employed. 'These are heavy and require large machineryto handle them, as will be apparent when it 'is recalled that some modern wells are over two miles deep. The power required to lift a lead cable two miles long is considerable.

Other mechanical difficulties, such as the cable breaking or the insulation becoming defective, have beenexperienced- Mereover, there are considerable electric losses in a long conductor, especially where'sepa'rated from the earth only a few inches, as in a well,

and these losses have made the currents supplied to the indicating instruments weak and unreliable.

It is an object of the present invention to b-- viate these difficulties by devising an arrangement for electrically logging an oil well or the like in which all conductors between instruments on the surface of the well and those in the well are dis- 7 pensed with.

. It is a further object of the invention to devise a self-contained unit in which all of the electrical In order to enable them to withfollowing description taken in connection with the accompanying drawing. in which:

Fig. 1 is an illustrationof a vertical cross-section of an oil well with apparatus constructed in accordance with the present invention mounted in and adjacent the well.

Fig. 2 is a diagram of an electrical system which illustrates one way of measuring the electrical properties of the formation of a well in accordance with the present invention.

Fig; 3 is a fragmentary view, partially in crosssection, of a portion of the casing and one electrode shown in Fig. 1; and

Fig. 4 is a view of a fragmentary portion of a chart on which characteristics of the formation of a well are recorded by apparatus like that diagrammatically shown in Fig. 2.

Referring to the drawing in detail, and first to the illustration of Fig. 1,-it will be seen that an'oil well is there illustrated at H. The well may be provided with a casing I! through a portion of its length, as illustrated in Fig. 1, but it will be apparent to those skilled in the art that the present invention is adapted for use in wells wholly cased, or those without any casing therein.

In accordance with the present invention, it is proposed to provide a self-contained and compact apparatus for logging the formation of the well. To this end, a strong casing I3 is provided and it is s6 constructed as tohouse and protect the electrical apparatus. Because the well may have a small bore,.the casing i3 should be only a few inches in diameter. In order to house all of the electrical apparatus it may be several feet in length, however.

At each end of the casing i 3 an electrode or antennae H is provided. Each electrode may be provided with a'hea'd portion l5 and be secured to the casing i3 by means of-end caps l6, one of which is shown in Fig. '3. It is preferable to insulate both electrodes from the casing l3 and from thecaps l8, but it is within the purview of the invention to have one electrode connected to the casing or, for that matter, to use the casing I3 itself as one of the electrodes.

\ In the arrangementillustrated, the electrode I4 is insulated from the cap l6 by means of insulation II, the lower portion of which may be clamped between the cap it and the head I! of the electrode.

The heads li'constitute terminals against which spring pressed connectors may abut to establish electrical contact with apparatus in the casing.

As illustrated in Fig. 2, the electrical apparatus contained within the casing [3, may consist of a simple electrical oscillating circuit vacuum tube circuit. This is illustrated as consisting of a variable condenser [8, a vacuum tube having a filament IS, a grid 20 and a plate 2 I, an A-battery 22, a B-battery 23, and an electrical indicating or recording instrument. The instrument 24 may be either a recording galvanometer, a. record,- ing frequency meter or the like.

In the arrangement illustrated in Fig. 2, an oscillating circuit may be set up and cause electrical impulses to be impressed upon the electrodes ll. Variations in the electrical characteristics, such as the di-electric strength of the formation adiacent the electrodes and around the casing l3, will, tunethe circuit to different frequencies and these variations may be recorded by the instrument 24.

The entire electrical system must be compactly assembled. Devices suitable for mounting in the confined space of the cylinder I 4 including a recording frequency meter are now known to those skilled in the art, however. Similar apparatus confined in a similar small space is disclosed in the co-pending application of Carl W; Cooper. Serial No. 137,835, filed April 19, 1937 for Logging devices.

For supporting the assembled electrical apparatus and electrodes, a steel tape or steel cable.

may be connected to the upper electrode H, as illustrated in Fig. 3. The steel tape 25 must be insulated from the electrode I4 and in the arrangement shown this is accomplishedby means of the insulator 26 of usual construction. It is preferable also to insulate both electrodes H from the oil, water or mud which may normally be in the well, and for this purpose the insulation I! has been shown extended and surrounding the joint between the electrode I4 and the steel tape 25. However, in cases where only the resistance of the formation is being indicated or recorded.

(as where a direct current system, such as a Wheatstone bridge is used), the electrodes M are only partly insulated or are not insulated at all.

The steel tape 25 may extend upwardly from the electrical unit and pass over a sheave 21 at the top of the well and from there pass through a measuring device 28, which may be of the type shown in the United States patent to Halliburton, No. 1,692,037. The measuring device may be provided with an indicator 29, to' show the number of feet of tape which has passed through and thus indicate the position of the electrical unit in the well. The apparatus also includes a reel or drum 30, around which the steel tape is wound, and also a suitable governor 3|, such as a centrifugal governor, the construction of which may be of any suitable type known to those skilled in the art,

which will cause the tape to move at a \gfigstant speed.

As disclosed in my co-pending application, Serial No, 106,352, filed October 19, 1936 for Method and means for measuring wells, it is possible to correlate the position of the electrical unit in the well and the particular characteristics of the formation recorded by the instrument 24, by means of the governor 3|. J

For example, assume that the instrument 24 makes a record on a tape like that illustrated at 32 in Fig. 4, and assume that the tape is driven at a constant speed by some suitable clock work. Assume that it is desired to log the oil well from a depth of 5,000 feet'to a depth of 6,000 feet. The unit may be lowered to the depth of 5,000 feet as indicated by the indicator 29 on the measuring device. If held stationary in this position I for a few minutes, substantially a straight line record will be made on the tape 32 of Fig. 4, as illustrated by the bracket 33. Since the apparatus is stationary, there will be no change in the electrical characteristic recorded during this time. When the apparatus is removed from the well, therefore, this point on the tape can be readily identified and it will be known that the record below the bracket 33 was taken when the electrical apparatus started tbtmove downwardly from the depth of 5,000 feet. If now the apparatus is moved downwardly at a constant speed, say 1,000 feet per hour, the time element can now be eliminated because the tape 32 is also moving at a constant speed, say for example a distance represented by the bracket 34, in one hour. An inspection of the tape sho'ws, therefore, that the record made within the bracket 34 indicates variations in the electrical properties ofthe formation from 5,000 to 6,000 feet, and a unit distance on the tape is equal to a unit distance in the well.

While only one embodiment of the invention hasbeen shown and described herein, it is obvious that various changes may be made without departing from the spirit of the invention orthe scope of the annexed claim; I

I claim:

, An arrangement for electrically logging an oil well or the like, including a cylindrical casing, a pair of electrodes, on mounted on each end of said casing, and elect cal devices and an indicating instrument mounted within said casing, the entire electrical apparatus being self-contained and adapted to be lowered into the well as a unit to measure and indicate an electrical property of the formation of the well located between said electrodes.

' EARL BABCOCK. 

